The present invention relates to an apparatus for diagnosing each fault portion in an automobile air-conditioning system.
In an automobile air-conditioning system, a blower and an air-mix door are controlled automatically so that an in-car temperature becomes a set temperature based on detected information from various sensors and operational information from an operation unit. Therefore, if any abnormalities occur in these sensors and operation units, then the desired air-conditioning would be unable to perform. The troubleshooting operation to find each fault portion is generally done by checking component factors of an electric system, by using a diagnosing device such as a tester and by using the experience of a repairman and maintenance manual. If a fault portion presents any abnormality during troubleshooting operation, it is easy to find the fault portion by the above manner. However, in the case of an imperfect contact or a half-disconnection, the abornormality does not always show and often does not repeat. Consequently, it sometimes occurs that such an abnormality does not appear at the time of the troubleshooting operation. In such case it is not possible to find the abnormality in spite of its existence.
Japanese Utility Model Laid Open Publication No. 56-67505 discloses an apparatus for diagnosing inconsistent and non-repeatable fault portions. This apparatus detects each diagnosed portion in which an abnormality occurs, stores each detected diagnosed portion in a nonvolatile memory, reads out the contents of said memory when a key switch is turned on, and displays each detected diagnosed portion. Since a diagnosed portion having an abnormality that occurs even once is stored in the nonvolatile memory, it is possible to know fault diagnosed portions having an abnormality that is inconsistent and non-repeatable.
However, the prior diagnosing apparatus has disadvantages as described below.
According to the prior diagnosing apparatus, a diagnosed portion, even when the diagnosed portion is normal, will be diagnosed to be a fault portion. That is to say, when the diagnosed portion is dismounted and remounted due to inspections or checkings, a malfunction that occurs during such dismounting and remounting operations is detected, and the diagnosed portion is diagnosed as the fault portion. Namely, since it is not possible to distinguish dismountings/remountings from true faults, even mere dismountings/remountings of diagnosed portions done during inspecitions or checkings will be diagnosed as faults.
Also, according to the prior diagnosing apparatus, diagnosed portions, which have any abnormalities occurring when the key switch is turned on, are displayed without being distinguished from other diagnosed portions which have abnormalities that occur before the key switch is turned on but do not repeat when the switch is turned on. Consequently, it is not possible to know if the diagnosed portions displayed as abnormalities are fault portions, which occur during diagnosing, or fault portions, which occur before diagnosing and lack repeatability. If these facts can be distinguished, then checking and repairing can be based on an understanding of whether or not abnormalities lacking repeatability. Thereby, finding any cause of such abnormalities as well as applying suitable remedy measures can be facilitated.